The present invention relates to the technical sector of surgical instruments and more specifically relates to a surgical assembly for the placement of a cap in a pedicle screw, in particular for treatment of spinal pathologies.
In general, a spinal implant comprises at least two pedicle screws intended to be screwed on a variable anatomical element of the vertebra (e.g. lamina, pedicle, vertebral body) and a connection system (plate or rod) uniting the two pedicle screws to each other.
Using a threaded cap suited for screwing into the head of the pedicle screw and for holding a connecting rod in place is well known. The cap used comes either in the form of a single cap comprising an external thread, and a central recess for tightening comprising, for example, a connection for a star screw-bit, or else in the form of a double cap comprising an inner cap and an outer cap screwed one into the other. The inner cap comprises a central hollow for tightening and an outer thread, and the outer cap comprises an inner thread and an outer thread and recesses for tightening.
Instruments for placement of these caps are also known. These instruments form, for example, a set generally comprising the cap as such and a cap-holder. The instruments are in particular designed for surgical operations referred to as minimally invasive, during which the surgeon is unable to view the implants.
A surgical assembly comprising a cap and a cap-holder is known from the state of the art, in particular disclosed in the document US 2011166610. The cap-holder includes two elastic and diametrically opposed longitudinal branches surrounded by a sliding sleeve. The branches each comprise an inner tang opposite from each other. The cap comprises two diametrically opposed radial grooves arranged in an outer lateral wall of said cap. The two grooves each comprise a recess complementary to the tang of the branches, laid out toward the inside of the cap.
In order to carry the cap, the two branches enter, by deforming elastically, into the grooves with the tangs thereof by engaging in the complementary recesses for holding the cap. The sleeve of the cap-holder is slid toward the cap for preventing the elastic branches from separating from each other and locking the connection between the cap-holder and the cap.
A cap and cap-holder is also known, in particular disclosed in the document US 2012123431. The cap comprises a central recess with an inner annular groove. The cap-holder comprises a hollow sleeve having a plurality of longitudinal slits defining elastic branches. The elastic branches each comprise a bead extending towards the outside of the sleeve, able to come to house, by elastic deformation of the branches, inside the annular groove of the cap. With the insertion of a locking pin in the hollow sleeve, the connection between the cap-holder and the cap is locked by blocking the elastic branches from coming closer.
A disadvantage of the surgical assemblies from the prior art described above resides in the fact that they cannot adapt to the two cap types, single or double, by allowing both the screwing of the inner cap and the screwing of the outer cap. In fact, the state of the art described above does not allow the surgeon to exert through the cap-holder a meaningful tightening torque on the cap, whatever the type thereof.